Drug loaded core-sheath fibers have been proposed for a number of medical applications, including for the localized delivery of therapeutic agents within a patient's body. Core-sheath fibers have several advantages over other drug delivery means, including relatively constant drug release that can be sustained over hours, days or weeks with relatively low levels of burst release, as well as the ability to tailor drug release kinetics according to the methods described in Sharma. Core-sheath fibers also allow formulations of drugs, polymers, excipients and other materials that are difficult or not possible to formulate into a monofiber. Implanted electrospun core-sheath fibers also provide highly localized release of therapeutics with a relatively low likelihood of unwanted migration from the site of implantation.
Methods of manufacturing core-sheath fibers loaded with small molecules including drugs have been described, and are discussed in Palasis II and Pham. However, scalable industrial methods for loading core-sheath fibers with an important category of therapeutic agents—proteins and peptides—have not been described. This is due in part to the technical challenges associated with working with proteins (namely, maintaining their activity and stability during and after their incorporation into fibers) in a manner that is economically feasible for industrial-scale fiber production. What is need is a method for producing protein-loaded core-sheath fibers in which the protein remains physically and chemically stable and retains its activity both during storage and after delivery to a patient.